This program is intended to investigate those host responses which result in immunopathology during schistosomiasis mansoni, and to determine what immunoregulatory mechanisms may control these processes. The primary focus will continue to be on schistosome egg-induced granuloma formation and immune responses against the antigens of eggs (SEA). Studies are in progress on the suppressor T lymphocytes which develop during chronic schistosomiasis, as well as humoral control mechanisms. The schistosome egg-eosinophil interaction which we have described, will be further dissected in hopes of establishing the mechanism by which eosinophils destroy these eggs. Altered egg-induced lesions, which occur in T lymphocyte-depleted-infected, and acute-infected mice will be examined, and attempts will be made to prevent their development by presensitization and passive transfer techniques. The current studies have demonstrated a lymphokine link between specific cell-mediated immune activities and an activation of eosinophils. These observations, which concern the lymphokine eosinophil stimulation promoter (ESP) and lymphocyte-derived chemotactic activity for eosinophils, will be further defined and analysed in regard against schistosome eggs. BIBLIOGRAPHIC REFERENCES: Colley, D.G.: Eosinophils and Immune Mechanisms IV. Culture conditions, antigen requirements, production kinetics and immunologic specificity of the lymphokine eosinophil stimulation promoter. Cell. Immunol. 24:328-335, 1976. Colley, D.G.: Immunopathology of Schistosomiasis. in Recent Advances in Clin. Immunol. 1977, in press.